The primary source of irrigation in Tamil Nadu is:

Canals
Tanks
Groundwater
Rainwater harvesting

The primary source of irrigation in Tamil Nadu is canals. Canals are artificial waterways that are used to transport water from a source, such as a river or a reservoir, to an area where it is needed for irrigation. Canals are a very efficient way to irrigate large areas of land, and they are a major source of water for agriculture in Tamil Nadu.

Tanks are artificial reservoirs that are used to store water for irrigation. Tanks are typically built on hills or in valleys, and they are filled with water from rainfall or from rivers. Tanks are a traditional source of irrigation in Tamil Nadu, and they are still used by many farmers today.

Groundwater is water that is found beneath the surface of the earth. Groundwater is a major source of water for irrigation in Tamil Nadu, and it is used by both farmers and households. Groundwater is a renewable resource, but it can be depleted if it is not used carefully.

Rainwater harvesting is the collection and storage of rainwater for use in irrigation or other purposes. Rainwater harvesting is a sustainable way to collect water, and it is becoming increasingly popular in Tamil Nadu. Rainwater harvesting can be used to irrigate crops, to water livestock, and to meet household water needs.

In conclusion, the primary source of irrigation in Tamil Nadu is canals. Canals are a very efficient way to irrigate large areas of land, and they are a major source of water for agriculture in Tamil Nadu. Tanks, groundwater, and rainwater harvesting are also important sources of irrigation in Tamil Nadu.